Process of using a submerged combustion melter to produce hollow glass fiber or solid glass fiber having entrained bubbles, and burners and systems to make such fibers

ABSTRACT

Processes and systems for producing glass fibers having regions devoid of glass using submerged combustion melters, including feeding a vitrifiable feed material into a feed inlet of a melting zone of a melter vessel, and heating the vitrifiable material with at least one burner directing combustion products of an oxidant and a first fuel into the melting zone under a level of the molten material in the zone. One or more of the burners is configured to impart heat and turbulence to the molten material, producing a turbulent molten material comprising a plurality of bubbles suspended in the molten material, the bubbles comprising at least some of the combustion products, and optionally other gas species introduced by the burners. The molten material and bubbles are drawn through a bushing fluidly connected to a forehearth to produce a glass fiber comprising a plurality of interior regions substantially devoid of glass.

BACKGROUND INFORMATION

1. Technical Field

The present disclosure relates generally to the field of combustionfurnaces and methods of use, and more specifically to processes forproducing hollow glass fiber or glass fibers comprising bubbles using aturbulent submerged combustion melter, and burners for carrying out suchprocesses.

2. Background Art

In submerged combustion melting of glass and similar materials,combustion gases emitted from sidewall-mounted and/or floor-mountedburners are injected beneath the surface of a molten or partially moltenmass of material being melted in a melter vessel and rise upward throughthe molten or partially molten mass. The molten or partially molten massof material is a complex mixture of molten feed material (feed materialis commonly referred to as “batch” in the glass industry), unmeltedbatch, and gases from the burners and evolved gases from the reaction ofand/or decomposition of batch materials. Recycled glass or “cullet”, aswell as various waste materials of varying glass content (such asfiberglass batting or even loose fibers) may also be present. Thematerials are heated at a high efficiency via the intimate contact withthe combustion gases. Using submerged combustion burners producesturbulence of the molten material or partially molten material.Vibration of the burners and/or the melter vessel walls themselves, dueto sloshing of molten material, pulsing of combustion burners, poppingof large bubbles above or aside of submerged burners, ejection of moltenmaterial from the melt against the walls and ceiling of melter vessel,and the like, are possible.

Traditional methods of making hollow fibers employ a bushing and asource of air feeding the air into the molten glass as it passes througha bushing. U.S. Pat. No. 2,269,459 discloses using a tube for injectingair into molten glass discharging vertically downward from a vessel, thetube extending through a bushing on the bottom of the melter. Theinitial hollow fiber formed is then drawn through and heated in a burnerthat provides intense flame and heat to form a much smaller diameterhollow fiber. Bushings are described in a series of patents for makingfibers having intermittent hollowness along their length, as well ashollow glass fibers of more uniform hollowness, more ratio of ID/OD, andbetter concentricity of the central lumen. See U.S. Pat. Nos. 3,421,873;3,510,393; 3,268,313; 4,735,642; and 4,758,259. None of these patentsuse or discuss submerged combustion. None of the previous solutions haverecognized that submerged combustion produces a turbulent molten glassthat has approximately 40 percent by volume gas bubbles. In fact,traditional glass melting technologies seek to reduce bubble contentwhen making glass fibers, as it leads to frequent processing problemsdue to fiber breakage during drawing. Molten glass fining is called forto reduce or eliminate bubbles, the fining employing conditioningchannels that may be difficult and/or expensive to operate.

It would be a significant advance in the glass melting art to developprocesses of making hollow glass fibers, or solid glass fibers havingentrained bubbles therein, and apparatus and systems to make suchfibers.

SUMMARY

In accordance with the present disclosure, processes, systems, andapparatus for carrying out the processes are described that producehollow glass fibers, or solid glass fibers having entrained bubblestherein, using submerged combustion melters. The processes, systems, andapparatus described herein are relevant to the full range of glassprecursor materials that may be melted with submerged combustiontechnology, but are particularly well-suited for “glass batch”, as thatterm is defined herein.

A first aspect of this disclosure is a process comprising:

-   -   a) feeding at least one partially or wholly vitrifiable feed        material into a feed inlet of a turbulent melting zone of a        melter vessel comprising a floor, a ceiling, and a wall        connecting the floor and ceiling at a perimeter of the floor and        ceiling, the melter vessel comprising a feed opening in the wall        or ceiling and an exit end comprising a melter exit structure        for discharging molten material formed in the turbulent melting        zone;    -   b) heating the at least one partially or wholly vitrifiable        material with at least one burner directing combustion products        of an oxidant and a first fuel into the turbulent melting zone        under a level of the molten material in the zone, one or more of        the burners configured to impart heat and turbulence to at least        some of the molten material in the turbulent melting zone,        producing a turbulent molten material comprising a plurality of        bubbles suspended in the molten material, the bubbles comprising        at least some of the combustion products;    -   c) discharging the molten material comprising bubbles from the        melter vessel through the melter exit structure into a        forehearth; and    -   d) drawing the molten material comprising bubbles through a        bushing fluidly connected to the forehearth to produce a glass        fiber comprising a plurality of interior regions substantially        devoid of glass.

A second aspect of this disclosure is a process comprising:

-   -   a) feeding at least one partially or wholly vitrifiable material        into a feed inlet of a turbulent melting zone of a melter vessel        comprising a floor, a ceiling, and a wall connecting the floor        and ceiling at a perimeter of the floor and ceiling, the melter        vessel comprising a feed opening in the wall or ceiling and an        exit end comprising a melter exit structure for discharging        molten material formed in the turbulent melting zone;    -   b) heating the at least one partially or wholly vitrifiable        material with at least one burner directing combustion products        of an oxidant and a first fuel into the turbulent melting zone        under a level of the molten material in the zone, one or more of        the burners configured to impart heat and turbulence to at least        some of the molten material in the turbulent melting zone,        producing a turbulent molten material comprising a plurality of        bubbles suspended in the molten material, the bubbles comprising        at least some of the combustion products;    -   c) discharging the molten material comprising bubbles from the        melter vessel through the melter exit structure into a        forehearth;    -   d) drawing the molten material comprising bubbles through a        plurality of bushings producing glass fibers each comprising a        plurality of interior regions devoid of glass, the fibers having        substantially same outside diameter; and    -   e) controlling flow of the molten material comprising bubbles        through the forehearth and bushings so that fibers produced        through the bushings are substantially consistent in volume of        regions devoid of glass.

A third aspect of this disclosure is a system comprising:

-   -   a) a melter vessel comprising a floor, a ceiling, and a wall        connecting the floor and ceiling at a perimeter of the floor and        ceiling, the melter vessel comprising a feed opening in the wall        or ceiling and an exit end comprising a melter exit structure        for discharging molten material formed in a turbulent melting        zone, and one or more burners, at least one of which is        positioned to direct combustion products into the turbulent        melting zone under a level of turbulent molten material in the        turbulent melting zone;    -   b) a forehearth fluidly connected to the melter exit structure        without any intervening channel or component, the forehearth        comprising a plurality of bushings configured to produce glass        fibers each comprising a plurality of interior regions devoid of        glass, the fibers having substantially same outside diameter.

A fourth aspect of this disclosure is an apparatus comprising:

a first conduit comprising a first end, a second end, a longitudinalbore having a longitudinal axis, and an external surface:

a second conduit substantially concentric with the first conduit, thesecond conduit comprising a first end, a second end, and an internalsurface;

the first and second conduits configured to form a primary annulusbetween the external surface of the first conduit and the internalsurface of the second conduit;

a third substantially concentric conduit comprising a first end, asecond end, and an internal surface, the internal surface of the thirdconduit forming, with an exterior surface of the second conduit, asecondary annulus external to the primary annulus;

a top end cap sealing the first ends of the second and third conduits,the second end of the second conduit sealed around the first conduit,and the second end of the third conduit sealed around the secondconduit, forming a cavity for fluid to circulate;

one or more passages near the second end of the second conduit forpassage of primary oxidant;

one or more alternate gas tubes extending substantially longitudinallythrough the secondary annulus and comprising distal ends terminating inat least one port near the first end of the second conduit; and

one or more secondary fuel tubes extending substantially longitudinallythrough the primary annulus and comprising distal ends positioned nearthe first ends of the first and second conduits.

A fifth aspect of this disclosure is an apparatus comprising:

a first conduit comprising a first end, a second end, a longitudinalbore having a longitudinal axis, and an external surface, the first endcomprising threads on the external surface,

a second conduit substantially concentric with the first conduit, thesecond conduit comprising a first end, a second end, and an internalsurface,

the first and second conduits configured to form a primary annulusbetween the external surface of the first conduit and the internalsurface of the second conduit;

a body having an upper surface, a lower surface, a circumferentialsurface abutting a portion of the internal surface of the secondconduit, and a generally cylindrical central hub concentric with thelongitudinal axis, the structure adjustable axially in relation to andthreadedly attached to the threads of the first end of the first conduitvia the hub, the hub defining a central passage having an exit at theupper surface, the body comprising one or more non-central throughpassages extending from the lower to the upper surface, the non-centralpassages configured such that flow of one or more fluids through thenon-central passages causes the fluids to intersect with a flow of oneor more other fluids in a mixing region above the upper surface of thebody;

a third substantially concentric conduit comprising a first end, asecond end, and an internal surface, the internal surface of the thirdconduit forming, with an exterior surface of the second conduit, asecondary annulus external to the primary annulus;

the first end of the third conduit extending beyond the first end of thesecond conduit, the first end of the second conduit extending beyond thefirst end of the first conduit, and the secondary annulus is capped byan end cap connecting the first end of the second conduit and the firstend of the third conduit; and

the second end of the second conduit sealed around the first conduit,and the second end of the third conduit sealed around the secondconduit, forming a cavity for fluid to circulate.

Processes, systems, and apparatus of this disclosure will become moreapparent upon review of the brief description of the drawings, thedetailed description of the disclosure, and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The manner in which the objectives of the disclosure and other desirablecharacteristics can be obtained is explained in the followingdescription and attached drawings in which:

FIGS. 1, 2, and 3 illustrate schematic side elevation views, partiallyin cross-section, of three system embodiments in accordance with thepresent disclosure;

FIGS. 4 and 5 illustrate schematic plan views, partially incross-section, of two system embodiments in accordance with the presentdisclosure;

FIGS. 6A and 6B illustrate schematic enlarged cross-sectional views oftwo different fibers made using the processes, systems, and apparatus ofthe present disclosure;

FIGS. 7 and 8 are schematic cross-sectional views of two apparatus inaccordance with the present disclosure;

FIGS. 7A and 8A are schematic plan views of the apparatus illustrated inFIGS. 7 and 8, respectively, while FIG. 8B is a cross-sectional view ofa component of the burner illustrated schematically in FIGS. 8 and 8A;and

FIGS. 9, 10, and 11 are logic diagrams illustrating processes inaccordance with the present disclosure.

It is to be noted, however, that the appended drawings are not to scaleand illustrate only typical embodiments of this disclosure, and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective embodiments.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of various, process, system, and apparatus embodimentsin accordance with the present disclosure. However, it will beunderstood by those skilled in the art that the melter apparatus andprocesses of using same may be practiced without these details and thatnumerous variations or modifications from the described embodiments maybe possible which are nevertheless considered within the appendedclaims. All U.S. published patent applications and U.S. patentsreferenced herein are hereby explicitly incorporated herein byreference. In the event definitions of terms in the referenced patentsand applications conflict with how those terms are defined in thepresent application, the definitions for those terms that are providedin the present application shall be deemed controlling.

Certain process embodiments may comprise controlling flow of the moltenmaterial comprising bubbles through the forehearth and bushings so thatfibers produced through the bushings are substantially consistent involume of regions devoid of glass. As used herein the phrase“substantially consistent in volume of regions devoid of glass” meansthat the fibers may be either random or non-random in the shape of theirvoid regions, but that the fibers nevertheless have about the samevolume of gas inclusions or bubbles. The gas inclusions or bubbles neednot be round, and may be oblong or irregular in shape.

Certain system embodiments may comprise a forehearth fluidly connectedto the melter exit structure without any intervening channel orcomponent. As used herein the phrase “without any intervening channel orcomponent” means the forehearth is directly connected to the melter exitstructure without any refining channel in between the melter exitstructure and forehearth. In certain embodiments, as explained furtherherein, a first forehearth may be fluidly connected to a secondforehearth by a distribution channel.

The phrase “at least one burner directing combustion products of anoxidant and a first fuel into the melting zone under a level of themolten material in the zone” as used herein means that combustion gasesemanate from burners under the level of the molten glass; the burnersmay be floor-mounted, wall-mounted, or in melter embodiments comprisingmore than one submerged combustion burner, any combination thereof (forexample, two floor mounted burners and one wall mounted burner). As usedherein the term “combustion gases” means substantially gaseous mixturesof combusted fuel, any excess oxidant, and combustion products, such asoxides of carbon (such as carbon monoxide, carbon dioxide), oxides ofnitrogen, oxides of sulfur, and water. Combustion products may includeliquids and solids, for example soot and unburned liquid fuels.

The phrase “turbulent melting zone” means that zone in a submergedcombustion melter wherein there is very turbulent, sometimesextraordinarily turbulent conditions inside the submerge combustionmelter. The phrase “turbulent molten material” means molten materialthat is in a condition of high turbulence, with many bubbles ofcombustion product gases and gases evolved from the glass batchmaterials becoming entrained in the molten material and some of thebubbles bursting as they reach the surface of the molten mass. This highdegree of turbulence can increase the mechanical load on the meltervessel walls significantly, especially in embodiments where some or allof the walls are fluid-cooled, as fluid-cooled wall structures may bemade thinner than non-cooled walls since the frozen or highly viscousglass layer formed thereon protects the walls better than non-cooledwalls. Therefore, while there may be savings in cost of materials forsubmerged combustion melter vessels with thinner, fluid-cooled walls,and fuel savings due to better heat transfer to the melt, there may beadverse physical impacts on the melter structure due to the very highturbulence imparted during submerged combustion.

The phrase “glass batch” as used herein refers to the initial rawmaterial, or glass source material, and may include any materialsuitable for forming molten glass such as, for example, limestone,glass, sand, soda ash, feldspar and mixtures thereof. It is important torecognize the difference between the glass batch composition and theglass forming ingredients or components of the glass batch. See forexample “Glass Melting”, Battelle PNNL MST Handbook, U.S. Department ofEnergy, Pacific Northwest Laboratory, retrieved 2012 Apr. 20. In oneembodiment, a glass composition for producing glass fibers may be“E-glass,” which typically includes 52-56% SiO₂, 12-16% Al₂O₃, 0-0.8%Fe₂O₃, 16-25% CaO, 0-6% MgO, 0-10% B₂O₃, 0-2% Na₂0+K₂O, 0-1.5% TiO₂ and0-1% F₂. Other glass compositions may be used, such as those describedin assignee's published U.S. applications 20070220922 and 20080276652.The initial raw material to provide these glass compositions can becalculated from information such as in Table 1, reproduced from theabove 20070220922 application. Notice that during glass melting, carbondioxide (from limestone (CaCO₃) and water (from borax (Na₂B₄O₇*10H₂O))evaporate.

TABLE 1 A typical E-glass batch BATCH COMPOSITION (BY WEIGHT) Quartz CaSilicate and Ca Limestone Quick- Ca Volcanic & Volcanic Quartz- Quartz-Limestone Ca Silicate Quartz- Clay Silicate/ Raw material (Baseline)lime Silicate Glass Glass free #1 free #2 Slag Slag free #3 FreeFeldspar Quartz (flint) 31.3% 35.9% 15.2% 22.6%  8.5%   0%   0% 22.3% 5.7%   0%   0% 19.9% Kaolin Clay 28.1% 32.3% 32.0% 23.0% 28.2% 26.4%  0% 22.7% 26.0% 26.0%   0%   0% BD Lime  3.4%  4.3%  3.9%  3.3%  3.8% 3.7%  4.3%  2.8%  3.1%  3.1%  4.3%  4.4% Borax  4.7%  5.2%  5.2%   0% 1.5%   0%   0%   0%   0%   0%  1.1%  1.1% Boric Acid  3.2%  3.9%  3.6% 7.3%  6.9%  8.2%  8.6%  7.3%  8.2%  8.2%  7.7%  7.8% Salt Cake  0.2% 0.2%  0.2%  0.2%  0.2%  0.2%  0.2%  0.2%  0.2%  0.2%  0.2% 0.2%Limestone 29.1%   0%   0% 28.7%   0%   0%   0% 27.9%   0%   0%   0%   0%Quicklime   0% 18.3%   0%   0%   0%   0%   0%   0%   0%   0%   0%   0%Calcium   0%   0% 39.9%   0% 39.1% 39.0% 27.6%   0% 37.9% 37.9% 26.5%26.6% Silicate Volcanic Glass   0%   0%   0% 14.9% 11.8% 17.0%  4.2%14.7% 16.8% 16.8%   0%   0% Diatomaceous  5.5% 17.4%   0%   0%  5.7%20.0%   0% Earth (DE) Plagioclase   0% 38.3%   0%   0%   0% 40.1% 40.1%Feldspar Slag   0%   0%  2.0%  2.0%  2.0%   0%   0% Total  100%  100% 100%  100%  100%  100%  100%  100%  100%  100%  100%  100% Volume of1668 0 0 1647 0 0 0 1624 0 0 0 0 CO2 @1400C

The term “air-fuel burner” means a combustion burner that combusts oneor more fuels with only air, while the term “oxy-fuel burner” means acombustion burner that combusts one or more fuels with either oxygenalone, or employs oxygen-enriched air, or some other combination of airand oxygen, including combustion burners where the primary oxidant isair, and secondary and tertiary oxidants are oxygen. Burners may becomprised of metal, ceramic, ceramic-lined metal, or combinationthereof. “Air” as used herein includes ambient air as well as gaseshaving the same molar concentration of oxygen as air. “Oxygen-enrichedair” means air having oxygen concentration greater than 21 mole percent.“Oxygen” includes “pure” oxygen, such as industrial grade oxygen, foodgrade oxygen, and cryogenic oxygen. Oxygen-enriched air may have 50 molepercent or more oxygen, and in certain embodiments may be 90 molepercent or more oxygen. Oxidants such as air, oxygen-enriched air, andpure oxygen may be supplied from a pipeline, cylinders, storagefacility, cryogenic air separation unit, membrane permeation separator,or adsorption unit.

The term “fuel”, according to this disclosure, means a combustiblecomposition (either in gaseous, liquid, or solid form, or any flowablecombination of these) comprising a major portion of, for example,methane, natural gas, liquefied natural gas, propane, atomized oil,powders or the like. Fuels useful in the disclosure may comprise minoramounts of non-fuels therein, including oxidants, for purposes such aspremixing the fuel with the oxidant, or atomizing liquid fuels. Theterms “first” or “primary” fuel, and “second” or “secondary” fuel meanthat the first fuel and second fuel have different compositions and/orphysical characteristics, although they may have overlapping components,and may have some similar physical characteristics. For example, naturalgas as a primary fuel may include some butane, and butane may beemployed as a secondary fuel. Tertiary fuels may also be used, that is,more than two fuels. The term “alternate gas” includes reactive gasesand inert gases, and mixtures thereof, substances that are gases atambient conditions, as well as compounds that are liquids at ambientconditions, but that vaporize at temperatures in a submerged combustionmelter, such as carbon disulfide. Reactive gases include, but are notlimited to, carbon dioxide, carbon monoxide, nitrous oxide, nitrousoxide, oxides of sulfur, fluorine, chlorine, silane, and the like. Inertgases include, but are not limited to, gases such as nitrogen, argon,xenon, and the like.

At least some of the burners may be floor-mounted, and in certainembodiments the floor-mounted burners may be positioned in one or moreparallel rows substantially perpendicular to a longitudinal axis of themelter. In certain embodiments, the number of floor-mounted burners ineach row may be proportional to width of the melter. In certainembodiments the depth of the melter may decrease as width of the melterdecreases. In certain other embodiments, an intermediate location maycomprise a constant width zone positioned between an expanding zone anda narrowing zone of the melter, in accordance with assignee's co-pendingU.S. patent application Ser. No. 12/817,754, filed Jun. 17, 2010,published as US 20110308280 on Dec. 22, 2011.

At least some of the burners may be oxy-fuel burners. In certainembodiments the oxy-fuel burners may comprise one or more submergedoxy-fuel combustion burners each having co-axial fuel and oxidant tubesforming an annular space there between, wherein the outer tube extendsbeyond the end of the inner tube, as taught in U.S. Pat. No. 7,273,583.In certain other embodiments the oxy-fuel burners may comprise one ormore adjustable flame submerged oxy-fuel combustion burners as taught inassignee's co-pending U.S. patent application Ser. No. 13/268,028, filedOct. 7, 2011. In certain embodiments, the burners may be modified asdescribed herein to provide one or more conduits or tubes for supplyinga secondary, tertiary or lower order fuel, or alternative gas species,to control or modify parameters of gaseous inclusions in the fibersproduced.

In certain embodiments, the melter apparatus may have a floor size for agiven throughput of 2 ft²/stpd or less, and in certain embodiment mayhave a floor size for a given throughput of 0.5 ft²/stpd or less, where“stpd” means “short tons per day.” Stated differently, in certainembodiments, the methods herein may comprise discharging at least 0.5short tons per day per square foot of melter floor, and in certainexemplary processes, at least 2 short tons per day per square foot ofmelter floor. The entrainment of one or more gases within the fibers mayreduce the amount of glass necessary to generate a specific length orvolumetric quantity of fiber, which may reduce the overall cost. Also,by utilizing glass that has a void fraction of gaseous bubbles forfiberization, the need for expensive and energy intensive downstreamequipment and processes to remove or “fine” the glass is unnecessary,resulting in improved capital costs.

Certain exemplary processes and systems of this disclosure may comprisecooling various components using fluid-cooled refractory panels anddirecting a heat transfer fluid through the panels. The term“fluid-cooled” means cooling using gaseous, liquid, or combinationthereof, heat transfer media. The wall may comprise a refractory linerat least between the fluid-cooled panels and the molten glass. Incertain embodiments, the refractory cooled-panels comprising the wallsof the melter vessel, the fluid-cooled skimmer, and fluid-cooled dams,may be cooled by a heat transfer fluid selected from the groupconsisting of gaseous, liquid, or combinations of gaseous and liquidcompositions that functions or is capable of being modified to functionas a heat transfer fluid. Different cooling fluids may be used in thevarious components, or separate portions of the same cooling compositionmay be employed in all components. Gaseous heat transfer fluids may beselected from air, including ambient air and treated air (for airtreated to remove moisture), inert inorganic gases, such as nitrogen,argon, and helium, inert organic gases such as fluoro-, chloro- andchlorofluorocarbons, including perfluorinated versions, such astetrafluoromethane, and hexafluoroethane, and tetrafluoroethylene, andthe like, and mixtures of inert gases with small portions of non-inertgases, such as hydrogen. Heat transfer liquids may be selected frominert liquids, which may be organic, inorganic, or some combinationthereof, for example, salt solutions, glycol solutions, oils and thelike. Other possible heat transfer fluids include steam (if cooler thanthe oxygen manifold temperature), carbon dioxide, or mixtures thereofwith nitrogen. Heat transfer fluids may be compositions comprising bothgas and liquid phases, such as the higher chlorofluorocarbons.

Conduits, tubes, and adjustable, changeable, removable bodies used inburners of the present disclosure may be comprised of metal, ceramic,ceramic-lined metal, or combination thereof. Suitable metals includestainless steels, for example, but not limited to, 306 and 316 steel, aswell as titanium alloys, aluminum alloys, and the like.

Referring now to the figures, FIG. 1 illustrates system embodiment 100comprising a melter having a floor 2, a roof or ceiling 4, a wall 6having a feed opening 18, and a feeder 20 for feeding batch, cullet,waste material, or combination thereof. System embodiment 100 furtherincludes an exhaust stack 8, and openings 10 for two (or more, notillustrated) floor-mounted and/or sidewall-mounted submerged combustionburners 12, which create during operation a highly turbulent meltindicated at 14, with a turbulent surface 15. In certain embodiments,floor-mounted burners 12 may be positioned to emit combustion productsinto molten glass in the melting zone 14 in a fashion so that the gasespenetrate the melt generally perpendicularly to floor 2. In otherembodiments, one or more floor-mounted burners 12 may emit combustionproducts into the melt at an angle to floor 2, where the angle may bemore or less than 45 degrees, but in certain embodiments may be 30degrees, or 40 degrees, or 50 degrees, or 60 degrees, or 70 degrees, or80 degrees. Burners 12 may be air-fuel burners or oxy-fuel burners, orsome combination thereof, or apparatus as further described in relationto FIGS. 7 and 8 herein. Embodiment 100 further includes a melter exitstructure 22 for discharging the molten glass or similar material 24including a plurality of gaseous bubbles 16 directly into a forehearth26. Melter exit structure 22 is positioned generally downstream ofmelter turbulent zone 14 as illustrated of FIG. 1, and may or may not bemechanically connected to forehearth 26. Importantly, no molten glassconditioning channel is included between melter exit structure 22 andforehearth 26. Completing system 100 are one or more bushings on a lowerportion of forehearth 26, system 100 having three bushings 28, 30, and32, for producing hollow fibers, or fibers having regions substantiallydevoid of glass. Examples of fibers producible using systems, processesand burner apparatus of this disclosure are illustrated schematically inFIGS. 6A-D.

System 100, and other systems of this disclosure, may comprise a sourcechamber for sourcing raw feed materials (for example glass batch) and afeed processing unit, such as described in assignee's United Statespatent application Ser. No. 13/540,704, filed Jul. 3, 2012. In theseembodiments, the source chamber defines an initial environment, whilefeed processing unit defines a second environment. In initialenvironment the feed materials are at a first density, while in secondenvironment the feed materials are transformed to have a second densitygreater than the first density, as well as having a degree ofcompaction, at least surface compaction, that work together to reducefines from escaping up melter exhaust 8 during operation of the systems.

The initial raw material may be introduced into, and molten glass withbubbles may be produced from the melters of systems of the presentdisclosure on a batch, semi-continuous or continuous basis. The amountof the initial raw material introduced into the melter is generally afunction of, for example, the capacity and operating conditions of themelter as well as the rate at which the molten material is removed fromthe melter.

The initial raw material may include any material suitable for formingmolten glass such as, for example, glass batches comprising combinationsof limestone, sand, trona, lime, albite, orthoclase dolomite, borax,soda ash, feldspar, and the like, and mixtures thereof. In certainembodiments, the initial raw materials may include batch componentssuitable for producing “E-glass” fibers, which typically include 52-56%SiO₂, 12-16% Al₂O₃, 0-0.8% Fe₂O₃, 16-25% CaO, 0-6% MgO, 0-10% B₂O₃, 0-2%Na₂0+K₂O, 0-1.5% TiO₂ and 0-1% F₂. Other glass compositions may be used,such as those described in assignee's published U.S. application20080276652. The initial raw material can be provided in any form suchas, for example, relatively small particles.

Referring now to FIG. 2, system embodiment 200 illustrated schematicallyin FIG. 2 is similar to embodiment 100 illustrated schematically in FIG.1, except that forehearth 26A is angled at an incline angle “θ” tohorizontal, where incline angle θ may range from about 5 to about 45degrees, or from about 5 to about 25 degrees, or from about 5 to about20 degrees. The result is that a distal end 26B of forehearth 26A israised above a proximate end 26C. Forehearth 26A may either be installedat a permanent incline angle or variable incline angle, for example byusing adjustable components such as jack screws, hydraulic or pneumaticcylinders, and the like. Installing the forehearth at an incline angleenables more consistent bubble entrainment within the glass andtherefore more consistent hollow fiber production. Bubbles willgenerally rise within the molten glass, and the rate of bubble rise maybe numerically modeled. The incline angle θ of the forehearth 26A, alongwith geometric features of the forehearth and positioning of bushings28A, 30A, and 32A may be manipulated to maintain substantiallyconsistent void fraction within the fibers produced. Geometric featuresthat may be manipulated include, but are not limited to, the inclineangle, the length and width of the forehearth, glass depth in theforehearth as a function of length along the forehearth, the angle tohorizontal of bushings, and the like. In embodiment 200, bushings 28A,30A, and 32A are each level to horizontal, but this is not necessarilyso. Surprisingly, contrary to common sense, the production rate ofhollow fibers is not greatly affected by increasing the incline angle.

System embodiment 300 illustrated schematically in FIG. 3 is similar toembodiments 100 and 200 illustrated schematically in FIGS. 1 and 2,except that embodiment 300 has its forehearth 26B positionedhorizontally, while bushings 28B, 30B, and 32B are positioned so thattheir inlets are successively higher toward distal end 27 than towardproximate end 29 of forehearth 26B. In this arrangement, as bubbles risein the molten glass as the molten glass travels through forehearth 26B,the fraction of bubbles in glass near the top of the molten glass shouldhave more bubbles than in the lower levels of the glass in forehearth26B. Therefore, fiber produced through bushing 28B should have morebubbles than fiber produced through bushing 30B, and fiber producedthrough bushing 30B should have more bubbles than fiber produced throughbushing 32B. In this way, fiber of varying void fraction may be producedusing the same feed material, melter and forehearth.

In certain systems and processes of the present disclosure, a frozenand/or highly viscous glass layer or layers may be formed on the insidesurfaces of wall 6 due to the use of fluid-cooled panels for thesewalls. One or more or all of wall 6, floor 2, and roof 4 may becomprised of a metal shell and a fluid-cooled refractory panel, notillustrated in the figures.

Melter exit structure 22 for discharging the molten glass or similarmaterial is provided in systems 100, 20, and 300. Melter exit structure22 may fluidly and mechanically connect the melter vessel to aforehearth 26, 26A, or 26B. Melter exit structure 22 may comprise afluid-cooled transition channel, having generally rectangularcross-section, although any other cross-sections would suffice, such ashexagonal, trapezoidal, oval, circular, and the like. Regardless ofcross-sectional shape, melter exit structure 22 may be fluid-cooled andconfigured to form a frozen glass layer or highly viscous glass layer,or combination thereof, on inner surfaces of structure 22 and thusprotect melter exit structure 22 from the mechanical energy impartedfrom the melter vessel to melter exit structure 22.

A fluid-cooled skimmer (not illustrated) may be provided, extendingdownward from the ceiling of the melter vessel and positioned upstreamof melter exit structure 22. A fluid-cooled skimmer, if present, mayhave a lower distal end extending a distance ranging from about 1 inchto about 12 inches (from about 2.5 cm to about 30 cm) below the averagemelt level in the melter. The fluid-cooled skimmer may be configured toform a frozen glass layer or highly viscous glass layer, or combinationthereof, on its outer surfaces. The skimmer lower distal end may define,in conjunction with the floor of the melter, a throat of the meltervessel configured to control flow of molten glass from the melter vesselinto melter exit structure 22. Preferably, the throat is arranged belowaverage melt level. Molten material can be removed from melter exitstructure 22 on a batch, semi-continuous basis or continuous basis. Inan exemplary embodiment, the molten material including a plurality ofbubbles continuously flows through the throat and generally horizontallythrough melter exit structure 22, and is removed continuously frommelter exit structure to a forehearth. Thereafter, the molten materialcan be processed by any suitable technique, for example, a process forforming hollow glass fibers.

Certain embodiments may include an overlapping refractory material layeron at least the inner surface of fluid-cooled transition channel thatare exposed to molten material. In certain embodiments the overlappingrefractory material may comprise a seamless insert of dense chrome,molybdenum, or other dense ceramic or metallic material. The densechrome or other refractory material may be inserted into the melter exitstructure and may provide a seamless transition from the melter vesselto a forehearth.

Referring to FIGS. 4 and 5, another optional feature of systems inaccordance with the present disclosure is the provision of one or morefluid-cooled dam(s) in the upper wall or ceiling of melt exit structure22, such as dams 42, 44 illustrated schematically in the plan view ofembodiment 400 in FIG. 4, and dams 60, 62 illustrated schematically inthe plan view of embodiment 500 in FIG. 5. The submerged combustionmelter (SCM) of embodiment 400 includes a feed end 34, a discharge end36, a partition 38, and a plurality of floor-mounted burners 12.Forehearth 26 includes an entrance end 40 and bushing 28, 30, and 32 forproducing E-glass of other glass fibers. Fluid-cooled dams 42, 44 wouldbe accommodated by respective dam openings (not illustrated in FIG. 4)in the roof or ceiling of the melter. System 500 illustratedschematically in FIG. 5 includes a first SCM 50, a second SCM 52, afirst forehearth 54 fluidly and mechanically connected to first SCM 50,and a second forehearth 56 fluidly and mechanically connected to secondSCM 52. First forehearth 54 is in turn fluidly and mechanicallyconnected to second forehearth 56 via a channel 58.

Embodiments 400 and 500 and those similar thereto may be employed toproduce fibers having different gaseous compositions of bubbles orregions devoid of glass. For example, referring again to FIG. 4, dam 42may be open while dam 44 is closed, and gas A may be injected into oneor more burners 12A, then dam 42 may be closed and dam 44 opened whilegas B may be injected into one or more burners 12B. Similarly, referringagain to FIG. 5, dam 60 may be open while dam 62 is closed, and gas Amay be injected into one or more burners 12A, then dam 60 closed and dam62 opened while gas B may be injected into one or more burners 12B.

Dams 42, 44, 60, and 62 may be manipulated by a prime mover, such as oneor more motors, jack screws, hydraulic or pneumatic cylinders or thelike. Fluid-cooled dams may comprise dimensions allowing the dam(s) tobe extended an entire distance from ceiling to floor of the melter andcompletely isolate the melting zones of the melter vessel from theforehearth.

FIGS. 6A and 6B illustrate schematically fiber embodiments 600 and 610,respectively that may be produced using processes, systems, andapparatus of the present disclosure. The illustrations are enlargementsof actual fibers. During production of the fiber, molten glass withentrained bubbles is extruded through orifices or nozzles in heatedbushings. During this process the molten glass and bubbles areattenuated (stretched) so that the generally spherical bubbles aretransformed into generally oblong shaped gaseous regions, 604. If thebubbles are large, the gaseous regions may form along the centrallongitudinal axis of the fiber and may appear as illustrated inembodiment 600 of FIG. 6A. If the bubbles are smaller, the gaseousregions may form generally randomly, radially away from the centrallongitudinal axis of the fiber, and may appear as illustrated in FIG.6B. Fiber outer diameter, “d₁” may range from about 4 micrometers toabout 40 micrometers, while the diameter of the gaseous regions, “d2”,may range from about 30 micrometers in embodiment 600 down to about 4micrometers in embodiment 610. Large fiber diameter d₁ will generallyallow larger gaseous region diameter, d₂, but the latter is highlydependent on the condition of the molten glass just prior to enteringthe bushing.

FIGS. 7 and 8 are schematic cross-sectional views of two apparatus inaccordance with the present disclosure, and FIGS. 7A and 8A areschematic plan views of the apparatus illustrated in FIGS. 7 and 8,respectively. FIG. 8B is a cross-sectional view of a component of theburner illustrated schematically in FIGS. 8 and 8A. Referring first toFIGS. 7 and 7A, apparatus embodiment 700 includes a top end plate 701, awater jacket/outer tube or conduit 702, a main or primary oxidantconduit 704, and a main or primary fuel conduit 706. Conduits 702, 704,and 706 are generally concentric about a central longitudinal axis “A1”,and create an outer or secondary annulus “A”, and an inner or primaryannulus “B”. In accordance with apparatus embodiment 700, one or moresecondary fuel conduits 708, 710 may be provided. Conduit 708 ispositioned in a thru-hole 718 in a second end plate 717, while conduit710 is similarly positioned in a thru-hole 720 in second end plate 717.Second plate 717 further comprises thru-holes 724, 726 for allowingprimary oxidant to pass into inner or primary annulus B. Optionalbrackets 732, 734 may be provided for structural support. Valves 738 maybe provided to control and/or adjust flow of secondary fuel throughconduits 708, 710.

As noted herein, in certain embodiments it may be beneficial to injectalternative, non-fuel gas species into molten glass produced by an SCM.One or more tubes or conduits 712, 714 may be provided for this purpose,as illustrated schematically in FIGS. 7 and 7A. Tubes or conduits 712,714 may terminate near the flow exit of annulus B in ports 713A, 713B,respectively, positioned in primary oxidant conduit 704. Conduits 712,714 may be positioned in thru-holes 722, 716, respectively, in a firstend plate 715. Optional valves 736 may be provided to control and/oradjust flow of alternate gas species through conduits 712, 714.Thru-holes 728, 730 allow a cooling fluid such as water to enter andexit outer annulus A for cooling. One or more valves 740 may be providedto control in-flow of primary fuel. FIG. 7A provides a schematic planview of apparatus embodiment 700. Of course, more or less than twoalternative gas species conduits may be provided, as may more or lessthan two secondary fuel conduits.

Referring now to FIGS. 8, 8A and 8B, an alternate apparatus embodiment800 includes an inner or first conduit 802 serving as a primary fuelconduit having an inlet 803, and an outer or second conduit 804 servingas a primary oxidant conduit having one or more inlet thru-holes 817,819 in a bottom plate 814. This arrangement may be more typical forair-fuel combustion, but oxy-fuel combustion is contemplated as well.Inner conduit 802 defines a longitudinal bore 806 having a longitudinalaxis A1, and inner conduit 802 and outer conduit 804 define a primaryannulus “B” between them. A third conduit 810 forms an outer body ofapparatus embodiment 800, with a cavity or secondary annulus “A” formedbetween third conduit 810 and second conduit 804. An end cap 813 definesan upper tip 811 of apparatus embodiment 800, which may be generallydoughnut-shaped, or other shape. End cap 813 may be integral with outerconduit 810 as illustrated, or may be a separate component attached toouter conduit 810 and inner conduit 804 via threads, screws, rivets, andthe like. Bottom plate 814 is included in embodiment 800, with slightstructural differences, and may include threads or other removablefastener to secure bottom plate 814 to conduit 804. Thru-holes 816, 818are provided in bottom plate 814 in embodiment 800 for accommodatingtubes or conduits 808 (for secondary fuel), 812 (for alternate non-fuelgas species), as well as coolant fluid inlet 820 and outlet 822 in outerconduit 810. Embodiments employing more than one coolant inlet and morethan one coolant outlet are considered within the disclosure, but maynot be necessary in all circumstances. Embodiment 800 may includes aplenum for delivering a fluid into primary annulus B, although a plenummay not be necessary in all embodiments. For example, where oxygen oroxygen-enriched gas is used as an oxidant, the present disclosurecontemplates embodiments where two or more oxygen supply conduits feedprimary annulus B.

Another component of burner embodiments of the present disclosure is anadjustable, changeable and removable structure or insert, designated 824in FIGS. 8, 8A, and 8B. Body 824 is adjustable in the sense that threads828 or other connectors to inner conduit 802 allow variation of theaxial position of insert 824. Furthermore, physical parameters of insert824 may be changed, as discussed herein. Finally, the entire insert maybe removed and replaced with another insert of same or differentdimensions if desired.

Insert 824 includes a body 833 having a central hub 826 that is, incertain embodiments, parallel to longitudinal axis A1, but notnecessarily so, hub 826 including a central passage having an exit 825that is, in certain embodiments, perpendicular to longitudinal axis A1,but not necessarily so. Body 833 includes an upper surface 836 and alower surface 838, and one or more non-central passages 834. In FIGS. 8and 8B, two of the non-central passages 834A and 834B are visible. Uppersurface 836 helps define, along with end cap 813, a mixing region 809where fluids emanating from central exit 825, which may be a fuelstream, and non-central passages 834, which may be oxidant streams, atleast partially mix. The streams may be switched in certain embodiments(in other words, fuel may traverse one or more non-central passages 834while oxidant emanates from central exit 825). In embodiments where theoxidant flows through the central passage, the flame shape may bebroader and the velocity of the combustion products lower in thevertical direction to enable more combustion and energy release lower inthe molten glass pool to enhance efficiency. Body 824 further includes acircumferential surface 837 that is adjacent a portion of the innersurface of second conduit 804, near the upper end of second conduit 804.

As illustrated in embodiment 800, body 824 may include a circumferentiallip 840 that abuts against an overhang portion 815 of end cap 813. Endcap 813 has a length or height L1, and lip 840 has a length L2 fromoverhang portion 815 to upper surface 836 of body 824, where L2 mayrange from about 0.25 inch to about 2 inches. Circumferential lipextension 840 extends away from upper surface 836 of body 824 andgenerally parallel to longitudinal axis L1. End cap 813 may extend aboveexit 825 of the substantially central passage of hub 826 a distance L1,which may range from about 0.5 inch to about 6 inches. Verticalconnector section 829 may have a length L3 ranging from about 0.25 inchto about 1 inch. As illustrated in FIG. 8B, exit 825 of thesubstantially central passage has a diameter L4. L4 may range from about0.25 inch to about 3.0 inches. Lengths L1, L2, L3, and L4 are parametersthat may be changeable and/or adjustable (as those terms are definedherein) in certain embodiments to achieve desired results, for exampleflame length, and may be interdependent. For example, length L1 may beadjustable and changeable, while lengths L2, L3, and L4 are onlychangeable from burner to burner.

Hub 826 includes, in embodiment 800, an angled or tapered section 827connecting exit 825 and a vertical connector section 829 that connectsangled section 827 with a threaded section 828. Threads on threadedsection 828 mate with corresponding threads 830 on an upper end 832 ofinner conduit 802. This threaded connection allows removal of insert 824and/or adjustment of burner parameters, as discussed further herein.

FIGS. 8 and 8B illustrate three angles α, β, and γ, one or more of whichmay be changeable features in burners of the present disclosure. As usedherein the word “changeable”, when referring to a burner feature, meansthat that feature may be physically different from burner to burner bymachining or molding, for example, while the term “adjustable” meansthat a feature of a burner may actually be varied without makingphysical modifications to the burner. Angle α is an angle that uppersurface 836 of body 833 makes with longitudinal axis L1, and may rangefrom about 45 to about 90 degrees. As illustrated in embodiment 800, incertain embodiments the non-central passages are generally linear andangled at an angle β measured from the longitudinal axis, the β angleranging from about 10 degrees to about 45 degrees. As illustrated inembodiment 800 of FIGS. 8 and 8B, the substantially central passage maycomprise an angled section 827 and a vertical connector section 829connecting angled section 827 with threaded section 828 of hub 826.Angled section 827 may form an angle γ to longitudinal axis L1 rangingfrom about 10 degrees to about 45 degrees.

FIG. 8B is a cross-sectional view of component 824 of an adjustable,removable component of the burners of FIG. 8 and taken along the lineB-B of FIG. 8A, which is a plan view of the same embodiment.

In certain embodiments, embodiment 800 may include one or more optionaltubes or conduits 823 for admitting a non-fuel gas species throughannulus A. A corresponding number of thru-holes or ports 823A would beprovided in these embodiments in a bottom portion 841 of conduit 810.

In embodiment 800, various constructions may be envisioned that wouldprovide the adjustment feature for adjustable component 824 and theoptions for introducing a secondary fuel and/or alternate non-fuel gasspecies. Tubes 808, 812 may be welded or brazed to component 824 so thatthe tubes line up with the non-central passages 834. Component 824 couldbe snuggly yet relatively loosely positioned inside of conduit 804, andthe whole weldment comprising component 824 and tubes 808, 812 rotatedas desired. Numerous other operable constructions would be possible andwithin this disclosure.

FIGS. 9, 10, and 11 are logic diagrams illustrating three non-limitingprocesses in accordance with the present disclosure. It should beemphasized that all steps of the various process embodiments need not becarried out in series or succession. Process embodiment 900 of FIG. 9includes the step of feeding at least one partially or whollyvitrifiable feed material into a feed inlet of a turbulent melting zoneof a melter vessel comprising a floor, a ceiling, and a wall connectingthe floor and ceiling at a perimeter of the floor and ceiling, themelter vessel comprising a feed opening in the wall or ceiling and anexit end comprising a melter exit structure for discharging moltenmaterial formed in the turbulent melting zone (box 902). Embodiment 900further includes heating the at least one partially or whollyvitrifiable material with at least one burner directing combustionproducts of an oxidant and a first fuel into the turbulent melting zoneunder a level of the molten material in the zone, one or more of theburners configured to impart heat and turbulence to at least some of themolten material in the turbulent melting zone, producing a turbulentmolten material comprising a plurality of bubbles suspended in themolten material, the bubbles comprising at least some of the combustionproducts (box 904). The process further comprises discharging the moltenmaterial comprising bubbles from the melter vessel through the melterexit structure into a forehearth (box 906), and drawing the moltenmaterial comprising bubbles through a bushing fluidly connected to theforehearth to produce a glass fiber comprising a plurality of interiorregions substantially devoid of glass (box 908).

Process embodiment 1000 of FIG. 10 includes the steps of feeding atleast one partially or wholly vitrifiable material into a feed inlet ofa turbulent melting zone of a melter vessel comprising a floor, aceiling, and a wall connecting the floor and ceiling at a perimeter ofthe floor and ceiling, the melter vessel comprising a feed opening inthe wall or ceiling and an exit end comprising a melter exit structurefor discharging molten material formed in the melting zone (box 1002).The process further includes heating the at least one partially orwholly vitrifiable material with at least one burner directingcombustion products of an oxidant and a first fuel into the turbulentmelting zone under a level of the molten material in the zone, one ormore of the burners configured to impart heat and turbulence to at leastsome of the molten material in the turbulent melting zone, producing aturbulent molten material comprising a plurality of bubbles suspended inthe molten material, the bubbles comprising at least some of thecombustion products (box 1004). Process embodiment 1000 furthercomprises discharging the molten material comprising bubbles from themelter vessel through the melter exit structure into a forehearth (box1006), drawing the molten material comprising bubbles through aplurality of bushings producing glass fibers each comprising a pluralityof interior regions devoid of glass, the fibers having substantiallysame outside diameter (box 1008), and controlling flow of the moltenmaterial comprising bubbles through the forehearth and bushings so thatfibers produced through the bushings are substantially consistent involume of regions devoid of glass (box 1010).

Process embodiment 1100 of FIG. 11 includes the steps of Feeding atleast one partially or wholly vitrifiable material into a feed inlet ofa turbulent melting zone of a melter vessel comprising a floor, aceiling, and a wall connecting the floor and ceiling at a perimeter ofthe floor and ceiling, the melter vessel comprising a feed opening inthe wall or ceiling and an exit end comprising a melter exit structurefor discharging molten material formed in the turbulent melting zone(box 1102). Process embodiment 1100 further comprises heating the atleast one partially or wholly vitrifiable material with at least oneburner directing combustion products of an oxidant and a first fuel intothe turbulent melting zone under a level of the molten material in thezone, one or more of the burners configured to impart heat andturbulence to at least some of the molten material in the turbulentmelting zone, producing a turbulent molten material comprising aplurality of bubbles suspended in the molten material, the bubblescomprising at least some of the combustion products (box 1104).Embodiment 1100 further comprises discharging the molten materialcomprising bubbles from the melter vessel through the melter exitstructure into a forehearth (box 1106), drawing the molten materialcomprising bubbles through a plurality of bushings producing glassfibers each comprising a plurality of interior regions devoid of glass,the fibers having substantially same outside diameter (box 1108),controlling flow of the molten material comprising bubbles through theforehearth and bushings so that fibers produced through the bushings aresubstantially consistent in volume of regions devoid of glass (box1110), and controlling composition of the molten material by adjustingone or more parameters of one or more of the burners selected from thegroup consisting of composition of the first fuel, composition of theoxidant, composition of a third fluid injected through at least one ofthe burners, flow rate of the first fuel, flow rate of the oxidant, andflow rate of the third fluid, wherein the third fluid is selected fromthe group consisting of a second fuel, a second oxidant, a fluid otherthan a fuel or an oxidant, and combinations thereof (box 1112).

In operation of systems and processes of this disclosure, feed material,such as E-glass batch (melts at about 1400° C.), insulation glass batch(melts at about 1200° C.), and the like, is optionally processed in afeed processing unit as described, producing densified material, thenfed to the melter through a feed chute and melter inlet. Scrap in theform of glass fiber mat and/or insulation having high organic bindercontent, glass cullet, and the like may be separately fed to the melter.One or more submerged combustion burners are fired to melt the feedmaterials and to maintain a turbulent molten glass melt. Molten glassmoves toward melter exit, and is discharged from the melter directly toa forehearth having one or more bushings, producing the hollow fibers,or fibers having regions devoid of glass. Winders or choppers receivethe fibers, making continuous fiber or chopped fiber.

Glass fiber formation, or fiberization, involves a combination ofextrusion and attenuation. In extrusion, the molten glass passes out ofthe forehearth through one or more bushings made of an erosion-resistantplatinum/rhodium alloy with very fine orifices, from 200 to as many as8,000. Bushing plates are heated electronically, and their temperaturemay be precisely controlled to maintain a constant glass viscosity.Water jets may be used to cool the filaments as they exit the bushing atroughly 1204° C./2200° F. Attenuation is the process of mechanicallydrawing the extruded streams of molten glass into fibrous elementscalled filaments, with an outer diameter ranging from about 4 μm toabout 40 μm. A high-speed winder catches the molten streams and, becauseit revolves at a circumferential speed of ˜2 miles/˜3 km per minute(much faster than the molten glass exits the bushings), tension isapplied, drawing them into thin filaments.

Bushing nozzle diameter determines filament diameter, and the nozzlequantity equals the number of ends. A 4,000-nozzle bushing may be usedto produce a single roving product or the process can be configured tomake four rovings with 1,000 ends each. The bushing also controls thefiber yield or yards of fiber per pound of glass. The processes andsystems of the present disclosure allow production of more yards offiber per pound of glass, due to the existence of the regions devoid ofglass. (The metric unit, tex, measures fiber linear density; 1 tex=1g/km, and yield is the inverse, yd/lb.) A fiber with a yield of 1,800yd/lb (275 tex) would have a smaller diameter than a 56 yd/lb (8,890tex) fiber, and an 800-nozzle bushing produces a smaller yield than a4,000-nozzle bushing. The range of fiber diameter, or micronage, maybecome more varied as composite reinforcements have become morespecialized.

A chemical coating, or size, may be applied to the fibers. Size istypically added at 0.5 to 2.0 percent by weight and may includelubricants, binders and/or coupling agents. Lubricants help to protectthe filaments from abrading and breaking as they are collected and woundinto forming packages and, later, when they are processed by weavers orother converters into fabrics or other reinforcement forms. Couplingagents may cause the fiber to have an affinity for a particular resinchemistry, improving resin “wetout” and strengthening the adhesive bondat the fiber-matrix interface. Some size chemistries are compatible onlywith polyester resin and some only with epoxy while others may be usedwith a variety of resins.

The drawn, sized filaments may be collected together into a bundle,forming a glass strand composed of 51 to 1,624 filaments. The strand iswound onto a drum into a forming package that resembles a spool ofthread. The forming packages, still wet from water cooling and sizing,are then dried in an oven, and afterward they are ready to be palletizedand shipped or further processed into chopped fiber, roving or yarn.Roving is a collection of strands with little or no twist. An assembledroving, for example, made from 10 to 15 strands wound together into amulti-end roving package, may require additional handling and processingsteps. Yarn is made from one or more strands, which may be twisted toprotect the integrity of the yarn during subsequent processingoperations, such as weaving.

Combustion product gases (flue gases) exit through stack, or may berouted to heat recovery apparatus. If oxy-fuel combustion is employed insome or all burners, the general principle is to operate combustion inthe burners in a manner that replaces some of the air with a separatesource of oxygen. The overall combustion ratio may not change.Throughput of melter apparatus described in the present disclosure maybe 0.5 short ton per day per ft² of melter footprint (0.5 stpd/ft²) ormore, and in some embodiments 2 stpd/ft² or more. This is at leasttwice, in certain embodiments ten times the throughput of conventional(non-SC) melter apparatus.

Processes and systems of the present disclosure may be controlled in anumber of different manners. In certain embodiments a master controllermay be employed, but the processes and systems described herein are notso limited, as any combination of controllers could be used. Thecontroller may be selected from PI controllers, PID controllers(including any known or reasonably foreseeable variations of these), andmay compute a residual equal to a difference between a measured valueand a set point to produce an output to one or more control elements.The phrase “PID controller” means a controller using proportional,integral, and derivative features. In some cases the derivative mode maynot be used or its influence reduced significantly so that thecontroller may be deemed a PI controller. It will also be recognized bythose of skill in the control art that there are existing variations ofPI and PID controllers, depending on how the discretization isperformed. These known and foreseeable variations of PI, PID and othercontrollers are considered within the disclosure.

The controller may compute the residual continuously ornon-continuously. Other possible implementations of the processes andsystems of the present disclosure are those wherein the controller maycomprise more specialized control strategies, such as strategiesselected from feed forward, cascade control, internal feedback loops,model predictive control, neural networks, and Kalman filteringtechniques. The controller may receive input signals from, and provideoutput signals for, for example, but not limited to, the followingparameters: velocity of fuel entering a burner; velocity of primaryoxidant entering a burner; velocity of secondary oxidant entering aburner; mass flow rate of primary and/or secondary or tertiary fuelentering a burner; mass flow rate of primary oxidant entering a burner;temperature of a fuel entering a burner; temperature of primary oxidantentering a burner; mass flow rate of alternate gaseous species; pressureof primary oxidant entering a burner; humidity of primary oxidant; feedrate of material into the melter, flow rate of molten material out ofthe melter, mass flow rate of hot effluent exhaust, mass flow rates ofinput and output heat transfer fluids for fluid-cooled panels, and thelike. Burner geometry and combustion ratio are other examples of inputsignals.

Submerged combustion burner combustion (flame) temperature may becontrolled by monitoring one or more parameters selected from velocityof the fuel, velocity of the primary oxidant, mass and/or volume flowrate of the fuel, mass and/or volume flow rate of the primary oxidant,energy content of the fuel, temperature of the fuel as it enters theburner, temperature of the primary oxidant as it enters the burner,temperature of the effluent, pressure of the primary oxidant enteringthe burner, humidity of the oxidant, burner geometry, combustion ratio,and combinations thereof. Exemplary processes and systems of thedisclosure comprise a combustion controller which receives one or moreinput parameters selected from velocity of the fuel, velocity of theprimary oxidant, mass and/or volume flow rate of the fuel, mass and/orvolume flow rate of the primary oxidant, energy content of the fuel,temperature of the fuel as it enters the burner, temperature of theprimary oxidant as it enters the burner, pressure of the oxidantentering the burner, humidity of the oxidant, burner geometry, oxidationratio, temperature of the effluent and combinations thereof, and employsa control algorithm to control combustion temperature based on one ormore of these input parameters.

The term “control”, used as a transitive verb, means to verify orregulate by comparing with a standard or desired value. Control may beclosed loop, feedback, feed-forward, cascade, model predictive,adaptive, heuristic and combinations thereof. The term “controller”means a device at least capable of accepting input from sensors andmeters in real time or near-real time, and sending commands directly tocontrol elements, and/or to local devices associated with controlelements able to accept commands. A controller may also be capable ofaccepting input from human operators; accessing databases, such asrelational databases; sending data to and accessing data in databases,data warehouses or data marts; and sending information to and acceptinginput from a display device readable by a human. A controller may alsointerface with or have integrated therewith one or more softwareapplication modules, and may supervise interaction between databases andone or more software application modules.

The apparatus (sometimes referred to herein as burners) used forsubmerged combustion may provide an amount of heat which is effective tomelt the initial raw material to form the molten material, and tomaintain the molten material in its molten state. The optimaltemperature for melting the initial raw material and maintaining themolten material in its molten state can depend on, for example, thecomposition of the initial raw material and the rate at which the moltenmaterial is removed from the melter apparatus, and the composition offuels, oxidants, and alternative gas species. For example, the maximumtemperature in the melter apparatus can be at least about 1400° C.,preferably from about 1400° C. to about 1650° C. The temperature of themolten material can be from about 1050° C. to about 1450° C.; however,systems and processes of the present disclosure are not limited tooperation within the above temperature ranges. The molten materialremoved from the melter apparatus is typically a substantiallyhomogeneous composition, but is not limited thereto.

Submerged combustion burners useful in the systems and processesdescribed herein (and that are not modified as described herein forintroduction of alternative fuels and/or gaseous species) include thosedescribed in U.S. Pat. Nos. 4,539,034; 3,170,781; 3,237,929; 3,260,587;3,606,825; 3,627,504; 3,738,792; 3,764,287; 7,273,583, and assignee'sU.S. patent application Ser. No. 13/268,028, filed Oct. 7, 2011, all ofwhich are incorporated herein by reference in their entirety. Regardlessof the burner type selected, the general idea is for the burners toprovide heat energy to a bath of molten material and simultaneouslycreate a well-mixed, turbulent molten material. The burners function byfiring a burning gaseous or liquid fuel-oxidant mixture into a volume ofmolten material. The burners described in the 583 patent provide astable flame at the point of injection of the fuel-oxidant mixture intothe melt to prevent the formation of frozen melt downstream as well asto prevent any resultant explosive combustion, and constant, reliable,and rapid ignition of the fuel-oxidant mixture such that the mixtureburns quickly inside the molten material and releases the heat ofcombustion into the melt. Completion of the combustion process resultsin bubbles rising to the surface of the turbulent melt. The location ofthe injection point for the fuel-oxidant mixture below the surface ofthe melting material enhances mixing of the components being melted andincreases homogeneity of the melt. Thermal NO_(x) emissions are greatlyreduced due to the lower flame temperatures resulting from themelt-quenched flame and further due to insulation of the hightemperature flame from the atmosphere.

Melter apparatus useful in processes and systems in accordance with thepresent disclosure may also comprise one or more wall-mounted submergedcombustion burners, and/or one or more roof-mounted burners.Roof-mounted burners may be useful to pre-heat the melter apparatusmelting zone and may serve as ignition sources for one or more submergedcombustion burners. Melter apparatus having only wall-mounted,submerged-combustion burners are also considered within the presentdisclosure. Roof-mounted burners may be oxy-fuel burners, but as theyare only used in certain situations, are more likely to be air/fuelburners. Most often they would be shut-off after pre-heating the melterand/or after starting one or more submerged combustion burners. Incertain embodiments, all submerged combustion burners are oxy-fuelburners (where “oxy” means oxygen, or oxygen-enriched air, as describedearlier), but this is not necessarily so in all embodiments; some or allof the submerged combustion burners may be air-fuel burners.Furthermore, heating may be supplemented by electrical heating incertain embodiments, in certain melter and forehearth zones.

The total quantities of fuel and oxidant used by the combustion systemare such that the flow of oxygen may range from about 0.9 to about 1.2of the theoretical stoichiometric flow of oxygen necessary to obtain thecomplete combustion of the fuel flow. Another expression of thisstatement is that the combustion ratio may range from about 0.9 to about1.2, inclusive of the end numbers, and possibly higher or lower incertain embodiments. In certain embodiments, the equivalent fuel contentof the feed material must be taken into account. For example, organicbinders in glass fiber mat scrap materials will increase the oxidantrequirement above that required strictly for fuel being combusted. Inconsideration of these embodiments, the combustion ratio may beincreased above 1.2, for example to 1.5, or to 2, or 2.5, or evenhigher, depending on the organic content of the feed materials.

The velocity of the fuel in the various submerged combustion burnersdepends on the burner geometry used, but generally is at least about 15m/s. The upper limit of fuel velocity depends primarily on the desiredmixing of the melt in the melter apparatus, melter geometry, and thegeometry of the burner; if the fuel velocity is too low, the flametemperature may be too low, providing inadequate melting, which is notdesired, and if the fuel flow is too high, flame might impinge on themelter floor, roof or wall, and/or heat will be wasted, and/or batchfines may short-circuit the melter and escape through the stack (despitethe feed densification discussed herein) which is also not desired,and/or the degree of turbulence may so great as to be detrimental torefractory, or other materials of construction. High turbulence may alsoproduce an undesirably high amount of foam or bubbles in the melt thatcannot produce hollow fibers, or fibers having regions devoid of glass.

Those of skill in this art will readily understand the need for, and beable to construct suitable fuel supply conduits and oxidant supplyconduits, as well as respective flow control valves, threaded fittings,quick connect/disconnect fittings, hose fittings, and the like.

Melter apparatus useful in the various embodiments described inaccordance with the present disclosure may be constructed using onlyfluid-cooled refractory panels, with or without a thin refractory“glass-contact” liner. The thin refractory liner may be 1 centimeter, 2centimeters, 3 centimeters or more in thickness, however, greaterthickness may entail more expense without resultant greater benefit. Therefractory liner may be one or multiple layers. Alternatively, meltersdescribed herein may be constructed using cast concretes such asdisclosed in U.S. Pat. No. 4,323,718. The thin refractory liningsdiscussed herein may comprise materials described in the 718 patent,which is incorporated herein by reference. Two cast concrete layers aredescribed in the 718 patent, the first being a hydraulically settinginsulating composition (for example, that known under the tradedesignation CASTABLE BLOC-MIX-G, a product of Fleischmann Company,Frankfurt/Main, Federal Republic of Germany). This composition may bepoured in a form of a wall section of desired thickness, for example alayer 5 cm thick, or cm, or greater. This material is allowed to set,followed by a second layer of a hydraulically setting refractory castingcomposition (such as that known under the trade designation RAPID BLOCKRG 158, a product of Fleischmann company, Frankfurt am Main, FederalRepublic of Germany) may be applied thereonto. Other suitable materialsfor the refractory cooled panels, melter refractory liners, andrefractory block burners (if used) are fused zirconia (ZrO₂), fused castAZS (alumina-zirconia-silica), rebonded AZS, or fused cast alumina(Al₂O₃). The choice of a particular material is dictated among otherparameters by the melter geometry and type of glass to be produced.

Forehearths useful in the various embodiments described in accordancewith the present disclosure may be constructed using similar materialsas the melters, except that fluid-cooled panels are not typically used(however, their use is not ruled out). Suitable forehearths includethose available from Nikolaus Sorg Gmbh & Co. KG, Lohr am Main, Germany.

Although only a few exemplary embodiments of this disclosure have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel apparatus andprocesses described herein. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims. In the claims, no clauses are intended to be inthe means-plus-function format allowed by 35 U.S.C. §112, paragraph 6unless “means for” is explicitly recited together with an associatedfunction. “Means for” clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents, but also equivalent structures.

What is claimed is:
 1. A process comprising: a) feeding at least onepartially or wholly vitrifiable feed material into a feed inlet of amelting zone of a melter vessel comprising a floor, a ceiling, and awall connecting the floor and ceiling at a perimeter of the floor andceiling, the meter vessel comprising a feed opening in the wall orceiling and an exit end comprising a melter exit structure fordischarging molten material formed in the melting zone; b) heating theat least one partially or wholly vitrifiable material with at least oneburner directing combustion products of an oxidant and a first fuel intothe melting zone under a level of the molten material in the zone, oneor more of the burners configured to impart heat and turbulence to atleast some of the molten material in the melting zone, producing aturbulent molten material comprising a plurality of bubbles suspended inthe molten material, the bubbles comprising at least some of thecombustion products; c) discharging the molten material comprisingbubbles from the melter vessel through the inciter exit structure into aforehearth having a plurality of bushings connected to the forehearthproducing fibers of the same outside diameter, the process comprisingcontrolling flow of the molten material comprising bubbles through theforehearth and bushings so that fibers produced through the bushings aresubstantially consistent in volume of regions devoid of glass, thecontrolling comprising inclining the forehearth at an angle tohorizontal of no more than about 30 degrees to horizontal, the anglecausing a distal end of the forehearth furthest from the melter exitstructure to be raised above a horizontal plane, while a proximal end ofthe forehearth remains at a level equal to that of the melter exit; andd) drawing the molten material comprising bubbles through the bushingsto produce glass fibers comprising a plurality of interior regionssubstantially devoid of glass.
 2. The process of claim 1 comprisingcontrolling composition of the turbulent molten material and the bubblessuspended in the molten material by adjusting one or more of theburners.
 3. The process of claim 2 comprising adjusting one or moreparameters selected from the group consisting of composition of thefirst fuel, composition of the oxidant, composition of a third fluidinjected through at least one of the burners, flow rate of the firstfuel, flow rate of the oxidant, and flow rate of the third fluid.
 4. Theprocess of claim 3 wherein the adjusting one or more parameters iscomposition of a third fluid injected through at least one of theburners selected from the group consisting of feeding a compositioncomprising a second fuel, feeding a second oxidant, feeding a fluidother than a fuel or an oxidant, and combinations thereof.
 5. Theprocess of claim 1 comprising adjusting one or more of temperature ofthe molten material, flow rate of vitrifiable feed material, moltenglass discharge rate, and degree of turbulence of the molten material toachieve an average bubble diameter in the molten material that is lessthan a diameter of the drawn fibers.
 6. The process of claim 1comprising controlling volume of individual regions substantially devoidof glass by adjusting volume of individual bubbles in the moltenmaterial.
 7. A process comprising: a) feeding at least one partially orwholly vitrifiable material into a feed inlet of a melting zone of amelter vessel comprising a floor, a ceiling, and a wall connecting thefloor and ceiling at a perimeter of the floor and ceiling, the incitervessel comprising a feed opening in the wall or ceiling and an exit endcomprising a melter exit structure for discharging molten materialformed in the melting zone; b) heating the at least one partially orwholly vitrifiable material with at least one burner directingcombustion products of an oxidant and a first fuel into the melting zoneunder a level of the molten material in the zone, one or more of theburners configured to impart heat and turbulence to at least some of themolten material in the melting zone, producing a turbulent moltenmaterial comprising a plurality of bubbles suspended in the moltenmaterial, the bubbles comprising at least some of the combustionproducts; c) discharging the molten material comprising bubbles from themelter vessel through the melter exit structure into a forehearth; d)drawing the molten material comprising bubbles through a plurality ofbushings producing glass fibers each comprising a plurality of interiorregions devoid of glass, the fibers having substantially same outsidediameter; and e) controlling flow of the molten material comprisingbubbles through the forehearth and bushings so that fibers producedthrough the bushings are substantially consistent in volume of regionsdevoid of glass, the controlling comprising inclining forehearth at anangle to horizontal of no more than about 30 degrees, the angle causinga distal end of the forehearth to be raised above a horizontal plane,while a proximal end of the forehearth, remains at a level equal to thatof the melter exit.
 8. The process of claim 7 wherein the controllingcomprises the bushings drawing off the molten material comprisingbubbles in a configuration where a bushing most proximal to the melterexit structure draws at a lowest level in the forehearth and succeedingbushings draw molten material comprising bubbles at succeeding higherlevels in the forehearth.
 9. The process of claim 7 comprisingcontrolling composition of the molten material by adjusting one or moreof the burners.
 10. The process of claim 9 comprising adjusting one ormore parameters selected from the group consisting of composition of thefirst fuel, composition of the oxidant, composition of a third fluidinjected through at least one of the burners, flow rate of the firstfuel, flow rate of the oxidant, and flow rate of the third fluid. 11.The process of claim 10 wherein the adjusting one or more parameters isadjusting composition of the third fluid injected through at least oneof the feeding of the third fluid is selected from the group consistingof feeding a composition comprising a second fuel, feeding a secondoxidant, feeding a fluid other than a fuel or an oxidant, andcombinations thereof.
 12. A system comprising: a) a melter vesselcomprising a floor, a ceiling, and a wall connecting the floor andceiling at a perimeter of the floor and ceiling, the melter vesselcomprising a feed opening in the wall or ceiling and an exit endcomprising a melter exit structure for discharging molten materialformed in a turbulent melting zone, and one or more burners, at leastone of which is positioned to direct combustion products into theturbulent melting zone under a level of turbulent molten material in theturbulent melting zone; b) a forehearth fluidly connected to the meterexit structure without any intervening channel or component, theforehearth comprising a plurality of bushings configured to produceglass fibers each comprising a plurality of interior regions devoid ofglass, the fibers having substantially same outside diameter, theforehearth inclined at an angle to horizontal of no more than about 30degrees to horizontal, the angle causing a distal end of the forehearthfurthest from the melter exit structure to be raised above ahorizontal)lane, while a proximal end of the forehearth remains at alevel equal to that of the melter exit.
 13. The system of claim 12wherein at least one of the burners comprises: a first conduitcomprising a first end, a second end, a longitudinal bore having alongitudinal axis, and an external surface; a second conduitsubstantially concentric with the first conduit, the second conduitcomprising a first end, a second end, and an internal surface; the firstand second conduits configured to form a primary annulus between theexternal surface of the first conduit and the internal surface of thesecond conduit; a third substantially concentric conduit comprising afirst end, a second end, and an internal surface, the internal surfaceof the third conduit forming, with an exterior surface of the secondconduit, a secondary annulus external to the primary annulus; one ormore alternate gas tubes extending substantially longitudinally throughone of the primary and the secondary annuli and comprising distal endsterminating in ports near the first end of the second conduit; and oneor more secondary fuel tubes extending substantially longitudinallythrough one of the primary and secondary annuli and comprising distalends positioned near the first ends of the first and second conduits.14. The system of claim 13 wherein the burner comprises one or more flowcontrollers on the primary conduit, one or more of the alternate gastubes, and/or one or more of the secondary fuel tubes allowingadjustment of composition of the turbulent molten material and thebubbles suspended in the molten material.
 15. The system of claim 12wherein the melter vessel comprises: a wall separating the incitervessel into first and second turbulent melting zones; the firstturbulent melting zone comprising a first feed opening, a firstplurality of burners positioned to direct combustion products into thefirst turbulent melting zone under a level of first turbulent moltenmaterial in the first turbulent melting zone, a first melter exitstructure, and a first melting zone dam; the second melting zone furthercomprising a second feed opening, a second plurality of burnerspositioned to direct combustion products into the second turbulentmelting zone under a level of second turbulent molten material in thesecond turbulent melting zone, a second melter exit structure, and asecond melting zone dam; and wherein the first and second melter exitsstructures are fluidly connected to the forehearth.
 16. The system ofclaim 12 comprising: a first inciter vessel comprising a first feedopening, a first plurality of burners positioned to direct combustionproducts into a first turbulent melting zone under a level of firstturbulent molten material in the first turbulent melting zone, a firstmelter exit structure for discharging first molten material into a firstforehearth, and a first dam; a second melter vessel comprising a secondfeed opening, a second plurality of burners positioned to directcombustion products into a second turbulent melting zone under a levelof second turbulent molten material in the second turbulent meltingzone, a second melter exit structure for discharging second moltenmaterial into a second forehearth, and a second dam; and the firstforehearth fluidly connected to the second forehearth by a distributionchannel.